Mid-chassis or underbody plows and scrappers are well known vis. U.S. Pat. Nos. 4,031,966; 4,337,832. It is also known to provide scrappers that are positioned in pairs on a vehicle, between the front and rear tires vis. U.S. Pat. No. 4,665,636. In this latter arrangement, the scrappers are independently vertically adjustable in terms of the positions of the lower edges of the blades below the vehicle chassis.
It is also known to relieve the weight of a snowplow blade resting on a road surface through the controlled application of an hydraulically lifting force to the plow blade, vis U.S. Pat. No. 5,265,356. Alternately, it is known to position a light weight scrapper array vertically using two hydraulic cylinders, cf U.S. Pat. No. 4,553,608.
A further known arrangement in the field of plowing blade supports is to provide an air-cushioned positioning system that holds a plowing blade in an upright orientation until an obstruction is struck, whereupon the blade will "trip" to pass over the obstacle, cf U.S. Pat. No. 4,031,966.
In designing an underbody plow or scrapper it is desirable to provide adjustability to raise or lower the blade, to rotate the blade up and down at its outer ends about a horizontal axis that is generally pointed in the direction of motion and to angle the blade to the left and right about a vertical axis. It is also desirable when the plow blade is light, to provide a supplementary force-control mechanism that will apply a downward force to the plow blade to maintain it in contact with the surface being plowed with the appropriate level of pressure.
These features of control should ideally be achievable, in whole or in part, at minimal cost and with a minimal addition of weight to the vehicle. Fluid hydraulic systems are capable of serving in such applications, but they are relatively expensive and heavy.
It is therefore an object of the invention to provide an underbody blade support system that has features of adjustability combined with simplicity and low cost.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.